Indexing mechanism



Patented July 21, 1942 INDEXING MECHANISM Amos H. Bawley, Sn, and Winthrop 'lrlble, Cincinnatl, Ohio, assiznors to The Cincinnati Milling Machine 00., Cincinnati, Ohio, at corporation of Ohio Application July 31, 1939, Serial No. 287,512

10 Claims.

This invention relates to machine tools and more particularly to improvements in indexing mechanisms.

One of the objects of this invention isto contrive an indexing mechanism so that wear in the position determining means will be minimized.

Another object of this invention is to provide an indexing mechanism having improved automatic locking means. 7

A further object of this invention is to provide acomplete power operated indexing unit for general use having its own prime mover and control circuit.

Other objects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawingsforming a part thereof and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

Referring to the drawings in which like reference numerals indicate like or similar parts:

Figure 1 is a plan view partly in section and with other parts broken away of the indexing drive mechanism.

Figure 2 is a section on the line 2-2 of Figure 1.

Figure 3 is a detail section on the line 3-3 of Figure 1.

Figure 4 is a section on the line M of Fig ure 3.

Figure 5 is an expanded view of the control cam for the locking mechanism.

Figure 6 is a diagrammatic view of the electrical control circuit.

In Figure 1 of the drawings, the invention is exemplified in connection with a machine tool of the broaching type having a reciprocable breaching ram l movable in guideways it formed on a fixed part it of the machine, and

' the mechanism of this invention is utilized in.

this case for indexing a work supporting table 13 after each stroke of the broaching ram to suitably holding the work during the mac operation.

The table it is secured to the upper end of a vertical shaft l and to the lower end of the shaft is secured a Geneva plate 16 having four radial shaft 23, and a worm wheel 24 keyed to the shaft i9. 1

The shaft l9 also carries a spur gear 25 for rotating through an idler gear 26, the spur gear 2'! which is fixed to the locking assembly control cam 28 shown in Figures 3-and 4.

For the purpose of locating and locking the table l3 at its various stations, the table has a plate 29 secured to the underside thereof from the periphery of which extends four equally spaced locating bits 30. One of these bits is shown in Figure 3 and it will be. noted that the sides of it are provided with'hardened wear plates 3|.

The locating and locking mechanism is adapted control cam 28. As shown in Figure 3 the ac-' tuator 36 has an enlarged head 31, thereby providing two shoulders 38 and 39. Cooperating shoulders ill and M are formed on the plungers 32 and 33 respectively. Since the parts are shown in a table locking position in Figure 3, the manner of unlocking the table will be explained first.

Assuming the control cam 28 rotating in a direction to cause downward movement of the actuator 36, the first thing that happens is that the shoulder 39 engages the shoulder M of the 40 Ice plunger 33. An outer coil spring 42 is interpesed between the end of the actuator 3t and a laterally projecting lug $3 on the locking plunger 33, and during movement of the actuator to take up the lost motion between the shoulders, this spring will merely expand due to the fact that the plunger 33 remains fixed in its locking position, The locking plunger has a beveled face it which engages the inclined face 45 of a fixed hardened block 46 which serves as a wedge to force the locking member against the bit 38, thereby clamping the bit against the locating plunger 32.

' The locating plunger is held against lateral movement by the adjustable gib M which is inslots IT. A Geneva crank arm. l8 keyed to a tel-posed between the locating plunger and the fixed part 48 of the machine. The gib is vertically adjustable by a set screw 49 which serves to initially determine the position of the locating plunger.

It will thus be seen that the initial movement of the actuator 34 takes up the lost motion between the shoulders 39 and 4| and thereafter positively moves the locking plunger 33 downward.

After the locking plunger has been loosened the shoulder 38 engages the shoulder 40 and-positively moves the locating plunger downward so that both plungers now move downward simultaneously to a point below the bit 30, thus clearing the bit and permitting the next indexing movement of the table to take place.

The worm 22 is uni-directionally driven by the prime mover 2| in such a direction as to rotate the worm wheel 24 and the Geneva crank arm 18 in a counterclockwise direction as viewed in Figure 1. This means that the idler gear 26 is rotated in a clockwise direction and the final gear 21 is rotated in a counterclockwise direction. This determines the direction of rotation of the 'cam 28 which is counterclockwise as indicated by the arrow 50 in Figures 4 and 5.

This drive mechanism is, in effect, a one revolution mechanism in the sense that the prime mover 2| rotates the shaft I9 through one revolution effecting in sequence unlocking of the table, indexing 'of the table, locking of the table, and then trips a control mechanism to stop the prime mover.

Control is also provided whereby the actual movement of the table from one station to the next may be an inching or jogging movement, that is, intermittently started and stopped at the will of the operator, but after the table has reached the next station, means are provided indexing movement. Thus, once the table has completed its movement to a new station it will be automatically locked at that station regardless of whether the movement to that station was by automatic cycle or by inching under the control of the operator.

The ordinate 5| in Figure 5 indicates the starting position of the roller 35 and corresponds to the starting position of the crank arm l8 indicated in Figure 1.

As the crank arm l8 rotates counterclockwise from its starting position the cam 28 simultaneously rotates in the direction of arrow 50 as indicated in Figure 5, and the inclined portion 52 of the cam track 36 between ordinate 5| and 53 effects downward movement of the roller 35 and thereby of the actuator 34 to effect unlocking of the table in the manner previously described. The unlocking of the table will be completed substantially at the same time that the roller 20 enters the radial slot I! of the Geneva plate l6, and during the next 90 degrees of rotation of the shaft IS, the table will be rotated to its next station.

As is usual with such mechanisms, the shaft [9 carries a locking plate 54 which is integrally secured to the crank arm l8 as by a pin 55, Fig- The camtrack 35 is provided with, a straight portion 58 which serves to hold the plungers 32" .and 33 in an unlocked condition during the indexing movement of the table. When this movement has been completed and the roller 20 starts to leave the slot H, the cam track 36 is provided with an inclined portion 59 which becomes effective at this time to start the table locking operation. In other words, the two plungers 32 and 33 which are being held in engagement with the shoulders 38 and 33 of the actuator 34 by springs 42 and 60 respectively move simultaneously with the actuator.

The spring 50 is interposed between the head of the actuator and the end of a pin 6| which is freely guided in a hole formed in the lateral projection 43 of plunger 33. The upper end of plunger 8| engages the. underside of a lateral projection 62 of plunger 32. It will be noted that the shoulder 40 on the plunger 32 is cut further from the end of plunger 32 than the shoulder 4| is cut with respect to the end of plunger 33. Thus, during this period of simultaneous upward movement the plunger 32 will be leading the end of plunger 33.

This has been provided so that the plunger- 32 which is the locating plunger may get into position first and determine the location of the table and also provide the abutment against which the clamping plunger 33 is to lock or clamp the bit 30.

The simultaneous upwardmovement of both plungers continues until the lateral projection 52 of the locating plunger 32 engages the fixed stop plate 83. The shoulder 38 of the actuator 34 now moves away from the shoulder 40 and the locating plunger 32 'is held in position by the spring 60. With the locating plunger 32 now ,in position, the actuator and plunger 33 continue moving to complete the locking operation.

The length of movement of the actuator 34 is made longer than the possible movement of the locking plunger so that after the locking resistance has stopped the movement of the plunger, the actuator will continue a sufiicient distance to effect separation of the shoulders 39 and 4|, thus permitting compression of the spring 42 and additional compression of the spring 60, whereby both plungers are held in locking'position by the springs.

After the locking of the table has been completed the cam 28 completes its rotation to the starting position and this idling movement is utilized to operate certain controls to stop the prime mover and condition 'the control means' for the next cycle of operation.

In Figure 6 there is shown a control circuit having means therein for, initiating actuation of the prime mover, for stopping the prime mover automatically after one revolution of the mechanism, and for stopping the indexing portion of the cycle at will by the operator.

In this circuit the motor 2| is connectible to three power mains 64, and 65 by a starting switch 61 for normal rotation of the motor, and by a reversingswitch 58 for effecting reverse rotation of the motor, but the latter is only utilized herein for stopping purposes, as will be explained hereafter. The starting switch 61 has a starter which is connected by line 84, stop button 85,'

and line 86 to the power main 65. Thus, when the starting button is depressed interconnecting contacts 83 and M, a circuit is completed from power main 65 through line 86, stop button 85, line 84, starting button 82, line 88, relay coil 18, line 19 and overload switches 1I and 12 to the power main 68. A parallel circuit is also com-' pleted by the starting button through interconnection of contact 83 with contact 81, current flowing from contact 81 through line 88 and relay coil 89 to line 19 which leads to power main 64. Thus, by depressing the starting button the relay coils 18 and 89 are simultaneously energized to effect actuation of the respective armatures 16 and 98.

Armature 98 closes contacts 9| and 92 to establish a holding circuit for the relay coil 89 through line 93, line 84, stop button 85 and line 86 to the power main 65, the other end of the coil being connected to the power main 84. In addition, the relay armature 98 closes contacts 94 and 95 to establish a circuit from line 93 through line 96, branch 91. closed contacts 98 and 99 of switch I88, and line IM to contact I82 of relay 16. This makes it possible for the relay armature 16 to interconnect contact I82 with contact I83 and thereby establish a holding circuit for relay coil 18 through branch line I88.

In addition, the relay armature 16 interconnects contact 18 with contact I85, thereby closing a circuit from the starting switch coil 69 through line 13, interconnected contacts 18 and I85, line I86 to junction I81. When the starting button is closed the circuit is completed from junction I81 through line 88, the starting button 82, line 88, stop button 85 and line 86 to the power main 65. After the relay armature 98 closes and the start button 82 is released, the circuit remains completed but this time through interconnected contacts 91 and 92 of relay 98 and line 93, thereby by-passing the start button to line 84.

This will cause rotation of the shaft I9 and of the control cams I81, I88 and I89 which are keyed to that shaft. 'After the shaft I9 rotates through a predetermined angle, the lobe II8 on cam I88 passes out from under the end of switch III, permitting the switch to close contacts H2 and H3, and establish a circuit from line 96, which is connected to power main 65, through line II4 to relay coil- 5, the other end being connected through line 19 to power main 64. This causes actuation of the relay armature 11 interconnecting contact 15 with contact II6.

This closes a parallel circuit from starting .coil 69 and line 13 to line I86. After this circuit has been established the lobe I" on cam I81 opens the switch I88, thereby breaking the holding circuit from relay coil 18 which was created by the closing of contacts I82 and I83, whereby the relay armature 16 opens so that the control of the starting coil 69 isnow transferred to the relay II5 under control of the switch III. Since the holding circuit for coil H5 is through the stop button 85 by way of switch III, line" 96 and closed contacts 94, 95 this button may be-depressed at any time to open the circuit to relay coil H5 and thereby open the circuit to the starting coil 69 to stop the: indexing movement at-will.

Since, at the same time, this will break the holding circuit to relay coil 89, contacts 94 and 95 will open, so that upon release of the stop button, the circuit to relay coil II5 will not be reestablished. It thus becomes necessary to depress the start button in order to start the indexing again. y, I After the indexing mechanism has completed approximately 180 degrees of rotation the roller 28 is about to pass out of the groove I1 of the Geneva plate, and at this time,-a lobe I I8 on cam I89 closes the switch II9. This completes a circuit from the starting coil 69 through line 13, interconnected contacts I28-I2I and line I22 to the power main 65.

The purpose of this circuit is to short out the stop button 85, rendering it ineffective to stop the motor, whereby the remainder of the cycle will be completed automatically to insure that the table is locked.

At the end of the cycle, the lobe II8 on cam I88 opens switch I II and instantaneously thereafter the switch II9 passes off of lobe II8 to open contacts I28, IZI;

The opening of switch I I I, breaks, the holding circuit to relay coil H5, opening contacts 15 and H6, thus transferring the control of the starting coil to switch I I9 and when this switch opens, the starting switch opens also.

.In order to quickly stop the motor a plugging relay I23, closes contacts I24, I25, completing a circuit from power main 65 through line I2-6,

closed contacts I24, I25, line I21, and contacts I28, I29 which were closed when the starting switch opened, to the reverse switch actuating coil I38. This puts a surge of reversing current through the motor, but as soon as themotor stops, the plugging relay opens whereby the parts remain at rest.

There has thus been provided an improved indexing mechanism which is a complete unit having 'its own power operated means and control circuit therefor whereby the mechanism may be intermittently operated or allowed to execute a complete automatic cycle whereby the indexible part is moved from one station to the next and in which a locking mechanism has been provided which is adapted to position and lock the indexible part in such a manner that minimum wear of.the parts will occur, thereby insuring lasting accuracy of the mechanism.

What is claimed is:

1. In an indexing mechanism for an indexible part of a machine tool, the combination of an indexible shaft for driving said part, means for locking said part, a second shaft for actuating said locking means, a drive shaft, a Geneva mechanism for transmitting motion from the drive shaft to the indexible shaft, a motion transmitting train connecting the drive shaft to said second shaft, a prime mover coupled to the drive shaft, and control means for startin and stopping said prime mover including means associated with the drive shaft for stopping the prime mover after the drive shaft has completed one revolution.

2. In an indexing mechanismfor a movable part of a machine tool, the combination with means for effecting said indexing, of a locking assembly for said part including a bit carried by said part for movement therewith, an abutment member movable into the path of said bit, a'

abutment plunger for determining the station position of the indexible member, a locking plunger, a bit carried by the indexible member, and

cam means for actuating said plungers in a pre-' determined sequence to lock the bit between the locking plunger and said abutment plunger.

4. In an indexing mechanism for the movable part of a machine tool, said part carrying a locating bit, the combination of means for engaging and clamping said bit to determine the station position of said part including an abutment plunger, a locking plunger, a common actuating means for said plungers including means normally maintaining one of said plungers in advance of the other during movement to locking position, a positive stop for the locating plunger, and resilient connections whereby said locking plunger is moved into clamping position after the locating plunger has stopped.

5. In a mechanism for indexing the movable part of a machine, the combination of a drive shaft, a Geneva mechanism actuable by the drive shaft for indexing said part, means for, locking said part against movement, an electrical prime mover coupled to the drive shaft, an electrical control circuit for said prime mover, said drive shaft being operable during one revolution to sequentially effect unfastening of said locking means, indexing of the part, and fastening of thelocking means in the order named, and switch means in said circuit actuable by the drive shaft for stopping the prime mover after the shaft has made one revolution.

6. In a mechanism for indexing a movable part of a machine, the combination of a Geneva plate coupled to said part,'a drive shaft, a roller carried by the drive shaft for engaging said plate, a motor permanently connected for actuation of the shaft, a control circuit for the motor, means in said circuit for stopping the motor at will during engagement of the roller with saidplate, and additional means in said circuit operable by the shaft when the roller passes out of engagement with the plate to render said stop means inefifiiactive until the shaft has completed a revoluon. I

'7. In an indexing mechanism for an indelible part of a machine, the combination of a branch transmission for effecting the indexing of the part, a second branch transmission for actuating a locking mechanism for the part, a common drive shaft for said transmissions, a motor for rotating said shaft, a solenoid actuated starter switch for said motor, a control circuit for the solenoid 01. said switch including a plurality of relays, manual switches for controlling said relays to effect starting and stopping of said motor at will, a trip operable switch and cam means carried by said shaft for closing said switch after the indexing has been completed to short circuit said relays and render said manually operated switches ineffective until the second branch transmission has completed the locking of the indexible part.

8. In an indexing mechanism for a. movable part of a machine, the combination with means for effecting index movement of said part, of means for locking said part including a series of radially extending bits integral with said part, a station determining plunger and a locking plunger, and means to shift said piungers after each indexing movement to effect clamping of one of said bits between said plungers to locate 9. In an indexing mechanism for a movable part of a machine tool, said part carrying a series of integral locating bits, the combination of means for locking said part including a pair of plungers, cam operated means for sequentially shifting said plungers, the first of which is moved into the path of one of said bits and the other behind said bit, and means for causing the lastnamed plunger to clamp the bit against the firstnamed plunger.

10. In an indexing mechanism for the movable part of a machine too], said part carrying a locating bit, the combination of means for engaging and clamping said bit including a pair of plungers, a common actuatorfor shifting said plungers into position on opposite sides of said bit, means for causing one of said plungers to lock said bit against the other plunger and resilient means compressible by said actuator for apply- I 

